1. Field of the Invention
The invention generally relates to gas-plasma treatment of substrates. More specifically, the invention relates to preparing an implant for use in biological/biomedical applications by subjecting the substrate to a gas-plasma treatment.
2. Description of Related Art
Successful repair or replacement of damaged or diseased tissues, organs, or bones requires integration of donor tissue or an implant with a patient's body. While tissue from the patient or from another donor may be integrated more readily than an implant, tissue transplantation has a high rate of failure and is accompanied by a risk of disease transmission. In addition, donor tissue may be in short supply, and transplantation procedures may be expensive. Implants used as medical implants have therefore been increasingly investigated as alternatives to donor tissue.
Although implants circumvent some of the problems associated with donor tissue, the use of implants introduces other problems. An artificial or synthetic implant may be incompatible with the body and may not function as well as the original tissue. Since the surface properties of an implant generally govern the interaction of the implant with the body, rejection and other medical complications are often traced to incompatible implant surfaces. Inert implants, once thought to be desirable, are now known to cause surrounding growth of fibrous tissue, thereby inhibiting integration of the implant with a patient's body. Biocompatible implants are believed to reduce this and other adverse membrane-mediated cellular responses, such as infection, inflammation, blood coagulation, etc., related to the presence of foreign matter in the body. Thus, considerable attention has been directed toward increasing biocompatibility of implants through modification of implant surfaces to mimic functionally equivalent surfaces in the body.
Implants are typically made from metals, polymers, and ceramics. These materials, however, do not generally adhere to host tissue or coatings designed to enhance implant biocompatibility. Therefore, implant surfaces are often conditioned or treated to increase adhesion to the host tissue or to a desired coating composition. A purpose of such treatment is to enhance integration of an implant with adjacent host tissue. Successful surface modification results in an implant with surface characteristics that allow adhesion of a desired coating. Implants thus treated allow ingrowth, or integration of host tissue with the implant coating.
A goal of forming biocompatible implants is choosing the most effective treatment and coating for the intended application. Coatings typically include inorganic, polymeric, and biological coatings. Since endothelial cells form blood-surface interfaces in the human body, the attachment of endothelial cells to implant surfaces as a method of promoting integration of the implant and inhibiting adverse membrane-mediated cell responses of the host tissue has been studied.
U.S. Pat. No. 6,033,582 to Lee et al., which is incorporated by reference as if fully set forth herein, describes gas-plasma treatment of implant device surfaces to obtain desirable surface features that enhance and optimize adhesion of coating materials and/or tissue interactions with the surface of a medical implant device.
An improvement in implant technology involves using implants as a source of drugs, agents, or other active substances, such as growth factors, to assist in wound healing and aid ingrowth of host tissue. Although controlled release of a therapeutic substance has received some interest, these applications typically involve the immediate, unsustained release of the therapeutic substance.